Recently, a secondary battery, which can be charged and discharged, has been widely used as an energy source for wireless mobile devices. Also, the secondary battery has attracted considerable attention as a power source for electric vehicles (EV), hybrid electric vehicles (HEV) and plug-in hybrid electric vehicles (Plug-in HEV), which have been developed to solve problems, such as air pollution, caused by existing gasoline and diesel vehicles using fossil fuels.
Small-sized mobile devices use one or several battery cells for each device. On the other hand, middle or large-sized devices, such as vehicles, use a battery module having a plurality of battery cells electrically connected to one another because high power and large capacity are necessary for the middle or large-sized devices.
Preferably, the battery module is manufactured so as to have as small a size and weight as possible. For this reason, a prismatic battery or a pouch-shaped battery, which can be stacked with high integration and has a small weight to capacity ratio, is usually used as a battery cell of a middle or large-sized battery module. In particular, much interest is currently focused on the pouch-shaped battery, which uses an aluminum laminate sheet as a sheathing member, because the pouch-shaped battery is lightweight and the manufacturing costs of the pouch-shaped battery are low.
Also, a plurality of battery cells is combined to constitute a battery module. When overvoltage, overcurrent or overheat occurs at some of the battery cells, therefore, safety and operating efficiency of the battery module are deteriorated. For this reason, it is necessary to provide a unit to sense and control such overvoltage, overcurrent or overheat. Consequently, a voltage sensor is connected to the battery cells to confirm an operating state of the battery cells in real time or at predetermined intervals and control voltage of the battery cells. However, installation or connection of such a sensing unit complicates an assembly process of the battery module. In addition, a short circuit may occur due to a plurality of wires used to install or connect the sensing unit. Also, as the result of wide application of secondary batteries, the secondary batteries are used as a power source for vehicles. Consequently, it is necessary to provide a fixing unit to stably maintain a contact state of the sensing unit even when strong impact or vibration is applied to the sensing unit.
On the other hand, in a case in which a plurality of battery cells is used to constitute a battery module or a plurality of unit modules, each of which includes a predetermined number of battery cells, is used to constitute a battery module, it is generally necessary to provide a large number of members to achieve mechanical coupling and electrical connection between the battery cells or the unit modules. However, a process of assembling such members is very complicated. Furthermore, it is necessary to provide a space in which the members are coupled, welded or soldered to achieve mechanical coupling and electrical connection between the battery cells or the unit modules. As a result, overall system size is increased. The increase of the size is not preferred as previously described. Consequently, there is a high necessity for a battery module which is more compact and exhibits high structural stability.